CN112383224B

CN112383224B - BOOST circuit for improving transient response and application method thereof

Info

Publication number: CN112383224B
Application number: CN202011301127.9A
Authority: CN
Inventors: 张亮
Original assignee: Shenzhen Injoinic Technology Co Ltd
Current assignee: Shenzhen Injoinic Technology Co Ltd
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2021-09-28
Anticipated expiration: 2040-11-19
Also published as: CN112383224A

Abstract

The invention provides a BOOST circuit for improving transient response and an application method thereof, the circuit comprises a BOOST converter for generating an output voltage higher than an input voltage, a current sampling module for generating a current detection signal, a switching device for controlling on-off in a PWM modulation signal, a control unit for generating the PWM modulation signal under the action of a reference voltage, a voltage feedback signal of the output voltage, the current detection signal and a slope compensation voltage and generating a modulation signal with a preset duty ratio in a set time period, and an output voltage slope sampling module for sampling the falling slope of the output voltage in the off time of the switching device. The invention can reduce the time from the change of the inductance current to the final load current, thereby improving the transient response speed of the BOOST and ensuring the stability of the system.

Description

BOOST circuit for improving transient response and application method thereof

Technical Field

The invention relates to the technical field of power electronics, in particular to a BOOST circuit for improving transient response and an application method applied to the BOOST circuit.

Background

With the rapid development of consumer electronics in recent years, the load transient requirements on power supplies are increasing. The BOOST converter can realize the boosted output of voltage, and is a very wide converter in practical application, but the traditional BOOST converter has to have a crossing frequency less than half of the zero point due to the influence of the right half-plane zero point, so that the bandwidth of the BOOST converter is not very large, and the load transient response speed is very slow.

The patent application No. CN201510134253.2 discloses a BOOST circuit for improving transient response, which aims to solve the problem of transient response (only including light load to heavy load), when the load increases in transient state, a preset large duty ratio is generated, and 99% duty ratio signals are compared to fully charge the load capacitor, so as to reduce the drop of output voltage.

As shown in fig. 1, fig. 1 is a schematic diagram of improving transient response in this patent, in the diagram, BOOST adopts PFM/PWM dual-mode control, i.e., it works in PFM under light load and in PWM under heavy load, and the problem to be solved is the transient process of switching from PFM to PWM. The switching signal controls OSC _ ON _ dead to change the frequency to generate a large duty cycle signal, so that the inductor current rises rapidly during the transient increase. As shown in fig. 2, a significant reduction in transient kick-down voltage can be seen.

However, this patent has the following disadvantages:

(1) depending on the PFM/PWM switching signal, it can only be applied for switching from very light load to heavy load. It is required to know that the circuit works in the PFM mode only when the load is less than a certain value, and when the load exceeds the certain value, the circuit works in the PWM discontinuous mode, and at this time, the load is not large enough, and the transient undershoot problem also exists when the circuit is switched to a heavy load, which is a problem that the patent cannot solve.

(2) Adding a predetermined large duty cycle can be problematic, and when the duty cycle is added to be large, the heavy load current is not particularly large, which can cause the inductive current to be overcharged, i.e. too much energy is delivered to the output, which can cause the output voltage to be overshot; when the duty ratio is too small, the rising speed of the inductive current is very slow, the output can not obtain enough energy to undershoot, and the effect of greatly improving transient undershoot cannot be achieved.

(3) In fig. 1 and 2, the speed of the load transient is not fast, and the heavy load of the jump is not large enough, so that the output voltage rises during the time period when LX is high when the transient occurs, the speed of the load transient is much faster in practical application, and the heavy load of the jump is also likely to be large, so that the undershoot is more serious than that in the figure.

In conclusion, the patent has too many limited conditions, the practical application is very limited, and the practical value is greatly reduced.

The invention application with the patent application number of CN201910003125.2 discloses a method for improving transient response by adopting BoostDCDC with variable negative feedback frequency and transconductance, wherein dynamic current of the BoostDCDC dynamically changes along with power supply voltage, output voltage and load current, transconductance of an error amplifier dynamically changes, and a current backward flow circuit is dynamically enabled through transient overvoltage detection, so that the output voltage can quickly respond and recover to an adjustment value, and transient response speed of a chip is improved.

As shown in fig. 3, fig. 3 is a schematic diagram of improving transient response in this patent, in which a negative feedback dynamic current generating circuit converts the change of output voltage from transconductance operational amplifier to current, and then the current enters a frequency variable oscillator and a variable transconductance, so that the rapid duty ratio is changed when a transient occurs, and the effect of improving transient response is achieved.

Specifically, when the load transient current increases, the output voltage initially drops to a certain extent, then is converted into current by the negative feedback dynamic current generating circuit, the frequency of the oscillator is increased, and the transconductance of the variable transconductance EA is increased, so that the duty ratio is rapidly increased, the inductive current quickly exceeds the heavy load current value, and finally the undershoot of the output voltage is reduced. When the load transient current is reduced, the output voltage is increased to a certain extent at first, then the output voltage is converted into current by a negative feedback dynamic current generating circuit, the frequency of an oscillator and the transconductance of variable transconductance EA are reduced, so that the duty ratio is rapidly reduced, the inductive current is rapidly smaller than the light load current value, and meanwhile, when the output voltage exceeds a certain value, the circuit also allows the current to flow backwards, so the overshoot of the output voltage is further reduced.

Patent 2 can solve the problem of BOOST transient response speed better than patent 1, but also has the following disadvantages:

(1) the circuit design is complex, and not only needs to adjust the frequency and transconductance, but also needs to detect the backward flow current and the backward flow current counting.

(2) The negative feedback dynamic current generation circuit introduces a small signal into the loop while adjusting the frequency and transconductance of the large signal, so that the influence of the small signal on the stability of the loop must be considered, which increases the difficulty of loop design.

From the foregoing analysis, it can be seen that the improvement of the BOOST load transient response speed is finally reflected in shortening the change speed of the inductor current, i.e. reducing the time of t1, and the most direct way is to change the OSC frequency to preset a large duty ratio, as shown in patent 1, but it needs to control the switching signal of the PFM/PWM, and the large duty ratio is fixed and is therefore limited in practical application.

The method of patent 2 starts from changing the OSC frequency and the rising or falling speed of Vea, and the duty ratio is changed dynamically with the output voltage, so that the transient response speed of the load can be improved better, but the design of the loop becomes more complicated because the negative feedback dynamic current generating circuit introduces a new small signal component into the loop.

In addition, as shown in fig. 4, when the load current of the BOOST converter suddenly increases instantaneously, since the inductor current cannot suddenly change, the power supply thereof is smaller than the load demand, and therefore the output voltage starts to decrease, the divided voltage VFB of the output voltage will be smaller than the reference voltage VREF, and the output Vea of EA will increase, so as to increase the duty ratio of the PWM signal, and increase the inductor current, as shown in the time period t1, the inductor current is always smaller than the load current, and therefore the output voltage always decreases, and when the inductor current increases to be larger than the load current, the output voltage starts to increase and finally tends to be stable, as shown in the time period t 2. Therefore, the time period t1 is the main reason for determining the maximum undershoot of the output voltage, so that the time period t1 is shortened, and the rapid rise of the inductor current is the key for reducing the undershoot when the load jumps from a light load to a heavy load.

As shown in fig. 5, when the load current of the BOOST converter suddenly decreases, the inductor current cannot suddenly change, and the power supply is larger than the load demand, so the output voltage starts to rise, and the divided voltage VFB of the output voltage will be larger than the reference voltage VREF. The output Vea of EA will drop to decrease the duty cycle of the PWM signal, so that the inductor current will drop, as shown in the time period t1, the inductor current is always larger than the load current, and the output voltage will rise, and when the inductor current drops to be smaller than the load current, the output voltage will begin to drop and finally stabilize, as shown in the time period t 2. Therefore, it is known that the time period t1 is the main reason for determining the overshoot of the output voltage, and therefore, reducing the time period t1 to allow the inductor current to rapidly drop is the key to reduce the overshoot when the load jumps from a heavy load to a light load.

Due to the effect of the right half-plane zero point of the BOOST converter, the bandwidth of the BOOST is limited to be less than half of the right half-plane zero point, so that Vea rises and falls slowly, which results in that the duty ratio changes slowly during the transient change of the load, as shown in fig. 5 and 6, so that the change of the inductive current is slow, t1 takes a long time, and the maximum undershoot voltage and the overshoot voltage are large.

Disclosure of Invention

The invention mainly aims to provide a BOOST circuit capable of improving transient response of a circuit load so as to ensure system stability and improve transient response.

Another object of the present invention is to provide a method for applying a BOOST circuit, which can improve the transient response of the circuit load to ensure the stability of the system and improve the transient response.

In order to achieve the above-mentioned objective, the present invention provides a BOOST circuit for improving transient response, which includes a BOOST converter for generating an output voltage higher than an input voltage; the current sampling module is connected to the BOOST converter and used for generating a current detection signal; the switching device is connected to the BOOST converter and controls on-off according to a PWM (pulse width modulation) signal; the control unit is connected to the BOOST converter and used for generating a PWM (pulse-width modulation) modulation signal under the action of a reference voltage, a voltage feedback signal of an output voltage, a current detection signal and a slope compensation voltage and generating a modulation signal with a preset duty ratio in a set time period; and the output voltage slope sampling module is connected to the BOOST converter and is used for sampling the falling slope of the output voltage in the turn-off time of the switching device.

In a further scheme, the BOOST converter comprises a voltage input end and a voltage output end, the voltage input end is connected with an input voltage, the input voltage is processed by the BOOST converter and then is output by the voltage output end, the voltage input end is connected with an input capacitor, a first inductor and a switch power tube, and the voltage output end is connected with an output capacitor and an output load.

In a further scheme, the control unit comprises a logic control module, a driving module, an error amplifier and a voltage comparator, wherein a reverse phase input end of the error amplifier is connected with a voltage feedback signal, a non-phase input end of the error amplifier is connected with a reference voltage, an output end of the error amplifier is connected with a non-phase input end of the voltage comparator, a reverse phase input end of the voltage comparator is connected with a current detection signal and a slope compensation voltage, an output end of the voltage comparator is connected with the logic control module, and the logic control module is connected with the driving module.

In a further aspect, the output voltage slope sampling module includes an operational amplifier OP, a fet MN0, a fet MN0, a fet MN1, a fet MN2, a fet MP1, a fet MP2, a fet MP3, a fet MP4, and a fet MP5, a non-inverting input terminal of the operational amplifier OP is connected to the output voltage V0, an output terminal of the operational amplifier OP is connected to a gate of the fet MN0, a drain of the fet MN0 is connected to a drain of the fet MP1, a gate of the fet MP1 is connected to a gate of the fet MP2, a gate of the fet MP2 is connected to a gate of the fet MP3, a gate of the fet MP4 is connected to a gate of the fet MP5, a gate of the fet 1 is connected to a gate of the fet MN2, a source of the fet MN0 is connected to an I current source, And the drain of the field effect transistor MP2 and the drain of the field effect transistor MP4 are connected with a current source I, and the drain of the field effect transistor MP3 and the drain of the field effect transistor MN1 are connected with the current source I and the current source Im in the capacitor C1.

In a further scheme, the field-effect transistor MP1, the field-effect transistor MP2 and the field-effect transistor MP3 are sequentially connected to form a current mirror structure, the field-effect transistor MP4 and the field-effect transistor MP5 are connected to form the current mirror structure, a switch SW1 and a capacitor C2 are connected between the field-effect transistor MP4 and the field-effect transistor MP5, the field-effect transistor MN1 and the field-effect transistor MN2 are connected to form the current mirror structure, and a switch SW2 and a capacitor C3 are connected between the field-effect transistor MN1 and the field-effect transistor MN 2.

In a further scheme, the switching device is a power switching tube controlled by the PWM modulation signal to be turned on and off, and is connected to the current sampling module.

In a further aspect, the voltage feedback signal is generated by a feedback network, the feedback network is mainly formed by a resistor divider circuit, and the resistor divider circuit is connected to the voltage output terminal.

In order to achieve another object, the present invention provides an application method of a BOOST circuit for improving transient response, where the BOOST circuit employs the above BOOST circuit, and the method includes the following steps: according to the load change condition, the rising slope or the falling slope of the output voltage in the turn-off time of the switching device is dynamically sampled, the sampled rising slope or the sampled falling slope is converted into a current signal and then is discharged or charged for a compensation network of the output end of the error amplifier, the duty ratio is rapidly reduced or improved, the overshoot or the undershoot of the output voltage is reduced, and the transient response speed of the output is accelerated.

The further scheme is that when the load jumps from light load to heavy load, the output voltage slope sampling module samples the falling slope of the output voltage in the turn-off time of the switching device, converts the sampled falling slope into a current signal and then directly charges a compensation network of an output end signal Vea of the error amplifier, and the signal Vea is quickly pulled up, so that the duty ratio is quickly improved.

According to a further scheme, after the inductive current gradually rises and is larger than the load current, the output voltage does not fall within the turn-off time of the switching device, and the slope of the output voltage within the turn-off time of the switching device is sampled to be zero by the output voltage slope sampling module.

The further scheme is that when the load jumps from heavy load to light load, the output voltage slope sampling module samples the rising slope of the output voltage in the turn-off time of the switching device, converts the sampled rising slope into a current signal and subtracts a threshold value, and then the current signal is directly discharged for the compensation network of the output end signal Vea of the error amplifier, so that the signal Vea is rapidly pulled down, and the duty ratio is rapidly reduced.

In a further scheme, after the inductor current gradually decreases and is smaller than the load current, the output voltage is the rising slope of the switch device when the load is unchanged within the turn-off time of the switch device.

Therefore, the invention starts from changing the rising and falling speeds of the output end signal of the error amplifier, shortens the change speed of the inductive current, converts the change of the output load current into the internal current by detecting the change rate of the output voltage in a specific time period and directly charges and discharges the internal current for the compensation network of the output signal of the error amplifier, thereby not only rapidly improving the duty ratio, but also not introducing small signal components and further simplifying the circuit design.

Therefore, the invention converts the change of the inductive current into the internal current to charge or discharge the compensation network by sampling the slope of the output voltage, can accelerate the change of the signal Vea, and reduce the time from the change of the inductive current to the final load current, thereby improving the transient response speed of the BOOST.

Drawings

Fig. 1 is a schematic diagram of a BOOST circuit of the prior art.

Fig. 2 is a waveform diagram of a BOOST circuit of the prior art.

Fig. 3 is a schematic diagram of a prior art method of boosting a dc to improve transient response.

Fig. 4 is a waveform diagram of a BOOST converter of the prior art during heavy loading from light loading.

Fig. 5 is a waveform diagram of a BOOST converter of the prior art during a heavy load jump and a light load jump.

Fig. 6 is a schematic circuit diagram of an embodiment of a BOOST circuit for improving transient response according to the present invention.

Fig. 7 is a schematic diagram of the output voltage, the inductor current, and the power switch driving of the BOOST converter under different loads in an embodiment of the BOOST circuit for improving transient response of the present invention.

Fig. 8 is a schematic circuit diagram of an output voltage slope sampling module in an embodiment of a BOOST circuit for improving transient response according to the present invention.

FIG. 9 is a waveform diagram of a heavy-duty BOOST converter with light-duty jump in an embodiment of a BOOST circuit for improving transient response according to the present invention.

FIG. 10 is a waveform diagram of heavy load, skip and light load of the BOOST converter in the embodiment of the BOOST circuit for improving transient response of the present invention.

The invention is further explained with reference to the drawings and the embodiments.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. Also, the use of the terms "a," "an," or "the" and similar referents do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

A BOOST circuit embodiment for improving transient response:

referring to fig. 6, a BOOST circuit for improving transient response according to the present invention includes a BOOST converter for generating an output voltage higher than an input voltage; a current sampling module 10 connected to the BOOST converter for generating a current sense signal Vsense; the switching device is connected to the BOOST converter and controls the on-off of the BOOST converter according to a PWM (pulse width modulation) signal; and the control unit is connected to the BOOST converter and used for generating the PWM modulation signal under the actions of a reference voltage VREF, a voltage feedback signal VFB of an output voltage V0, a current detection signal Vsense and a slope compensation voltage Vslope and generating the modulation signal with a preset duty ratio in a set time period.

In this embodiment, the BOOST converter includes a voltage input end and a voltage output end, the voltage input end is connected to an input voltage Vin, the input voltage Vin is processed by the BOOST converter and then obtains an output voltage V0 through the voltage output end, the voltage input end is connected to an input capacitor Ci, a first inductor L, a switching power tube BG and a freewheeling diode D, and the voltage output end is connected to an output capacitor Co and an output load Ro. The capacitor C0, the capacitor C1 and the resistor Rc1 form a compensation network of the error amplifier EA.

In this embodiment, the control unit includes a logic control module 20, a driving module 30, an error amplifier EA and a voltage comparator CMP2, an inverting input terminal of the error amplifier EA receives the voltage feedback signal VFB, a non-inverting input terminal of the error amplifier EA receives the reference voltage VREF, an output terminal of the error amplifier EA is connected to a non-inverting input terminal of the voltage comparator CMP2, an inverting input terminal of the voltage comparator CMP2 receives the current detection signal Vsense and the slope compensation voltage Vslope, an output terminal of the voltage comparator CMP2 is connected to the logic control module 20, and the logic control module 20 is connected to the driving module 30.

In this embodiment, the switching device is a power switch BG controlled by the PWM modulation signal to be turned on or off, and is connected to the current sampling module 10.

In this embodiment, the voltage feedback signal VFB is generated through a feedback network, and the feedback network is mainly formed by a resistor divider circuit connected to the voltage output terminal. The resistor voltage divider circuit includes a predetermined number of voltage dividing resistors connected in series between the output terminal and the ground terminal, such as voltage dividing resistors R1 and R2, where the points connected between the voltage dividing resistors form voltage dividing nodes, and the voltage feedback signal VFB is led out from the voltage dividing nodes.

Referring to fig. 7, as shown in fig. 7(a), when the load is constant, when the power switch BG is turned on, the inductor current rises, the load is powered by the output capacitor Co, and thus the output voltage V0 drops slightly; when the power switch BG is turned off, the inductor current decreases, and its energy supplies the output capacitor Co and the load, so the output voltage V0 will increase slightly.

When the load jumps from a light load to a heavy load as shown in fig. 7(b), when the power switch BG is turned on, the inductor current rises, and the load is supplied by the output capacitor Co, so the output voltage V0 will drop faster than in fig. 7(a) (because the same load capacitor is supplied, but the load in fig. 7(b) is larger).

When the power switch tube BG is turned off, the inductive current supplies power to the load and the output capacitor Co, and the inductive current rises slowly and is smaller than the load current within a period of time, so that the output voltage V0 does not rise but falls, which is a place obviously different from the place shown in fig. 7 (a).

As shown in fig. 7(c), when the load jumps from a heavy load to a light load, when the power switch BG is turned on, the inductor current rises, the load is supplied by the output capacitor Co, and thus the output voltage V0 will drop more slowly than in fig. 7(a) (because the same load capacitor is supplied, but the load in fig. 7(c) is smaller).

When the power switch tube BG is turned off, the inductive current supplies power to the load and the output capacitor Co, and the inductive current is slowly reduced and is larger than the load current for a period of time, so that the output at the moment is more rapidly increased than that of a figure 7(a), which is obviously different from the figure 7 (a).

Therefore, the slope of the sampled output voltage V0 has a great advantage in that it can reflect the size of a jump load, for example, when the load jumps from a light load to a heavy load, the larger the heavy load value is, the larger the falling slope of the output voltage V0 in the BG off time is, and therefore, the larger the charging current of the compensation network for the signal Vea is, so that not only can the duty ratio change rate when the load jumps to different heavy loads be automatically adjusted to prevent the overshoot that occurs when the change is too fast, but also the duty ratio can be rapidly adjusted at the beginning of the falling of the output voltage V0, instead of the change of the sampled output voltage V0, the speed of adjusting the duty ratio at the beginning is very slow, and the duty ratio can be adjusted more rapidly after the output voltage V0 changes for a certain value. The same is true for the case of heavy load, jump and light load.

Therefore, in the present embodiment, an output voltage slope sampling module 40 is included, which is connected to the BOOST converter and is used for sampling the falling slope of the output voltage V0 during the off time of the switching device.

Referring to fig. 8, the output voltage slope sampling module 40 includes an operational amplifier OP, a fet MN0, a fet MN0, a fet MN1, a fet MN2, a fet MP1, a fet MP2, a fet MP3, a fet MP4, and a fet MP5, wherein a non-inverting input terminal of the operational amplifier OP is connected to the output voltage V0, an output terminal of the operational amplifier OP is connected to a gate of the fet MN0, a drain of the fet MN0 is connected to a drain of the fet MP1, a gate of the fet MP1 is connected to a gate of the fet MP2, a gate of the fet MP2 is connected to a gate of the fet 3, a gate of the fet MP4 is connected to a gate of the fet MP5, a gate of the fet 1 is connected to a gate of the fet MN2, a source of the fet MN0 is connected to a current source I, a capacitor C1, a drain of the fet MP2 and a drain of the fet MP4 are connected to a current source I, the drain of the field effect transistor MP3 and the drain of the field effect transistor MN1 are connected to a current source I and a current source Im.

The field-effect transistor MP1, the field-effect transistor MP2 and the field-effect transistor MP3 are sequentially connected to form a current mirror structure, the field-effect transistor MP4 and the field-effect transistor MP5 are connected to form the current mirror structure, a switch SW1 and a capacitor C2 are connected between the field-effect transistor MP4 and the field-effect transistor MP5, the field-effect transistor MN1 and the field-effect transistor MN2 are connected to form the current mirror structure, and a switch SW2 and a capacitor C3 are connected between the field-effect transistor MN1 and the field-effect transistor MN 2.

Specifically, the current source I is a fixed current source, and is mainly used for providing a bias current for the circuit to establish a direct current operating point; the field effect transistors MP1, MP2, and MP3 form a current mirror structure, the field effect transistors MP4 and MP5 also form a current mirror structure, the switch SW1 is turned on when the power switch BG is turned off, and the capacitor C2 is a sample hold capacitor. When the current source Im is a load and is not in motion, the output voltage when the power switch tube BG is turned off rises by a slope preset current, the field effect tube MN1 and the field effect tube MN2 form a current mirror structure, the switch SW2 is also turned on when the power switch tube BG is turned off, and the capacitor C3 is also a holding capacitor.

In practical applications, the output voltage slope sampling load change is converted into current entering the fets MP2 and MP 3. When the power switch tube BG is turned off, the switches SW1 and SW2 are conducted, when a load is converted from a light load to a heavy load, the currents of the field effect tubes MP2 and MP3 are smaller than I, so that the load current is changed and enters the field effect tube MP4, no current is generated in the field effect tube MN1, the current of the field effect tube MP4 is mirrored by the field effect tube MP5 and charges a compensation network of a signal Vea, and the duty ratio can be rapidly increased; when the load jumps from heavy load to light load, the current of the field effect transistor MP2 is greater than I, the current of the field effect transistor MP3 is greater than I + Im, so that the load current changes and enters the field effect transistor MN1, no current is generated in the field effect transistor MP4, the field effect transistor MN2 mirrors the current of the field effect transistor MN1 and discharges the current to a compensation network of a signal Vea, and the duty ratio can be rapidly reduced; when the load is not in motion, the current of the fet MP2 will be greater than I, and the current of the fet MP3 will be greater than I but less than Im, so that neither the fet MP4 nor the fet MN1 will generate current, and this circuit will not have current entering the compensation network of the signal Vea, and will not affect the loop stability when the load is not in motion.

Specifically, for fig. 6, when the load changes, as in equation (3.1):

wherein, Co is the output capacitance,

the Δ Io is the change in load for the change slope of the output voltage V0.

For fig. 8, when the load changes as in equation (3.2):

formula (3.3) can be obtained from formula (3.1) and formula (3.2):

it can be seen that the change in load current can be converted to a current Δ Is by sampling the output voltage V0. When the power switch tube BG Is turned off, if the load jumps from a light load to a heavy load, the delta Is negative, so that the current of the field effect tube MP4 Is I-I-delta Is, the field effect tube MP5 mirrors the current to charge the compensation network, and the field effect tube MN1 does not generate current; if the load jumps from heavy load to light load, the delta Is positive, so that the current of the field effect transistor MN1 Is I + delta Is-I_m＝ΔIs-I_mThe fet MN2 will mirror this current to discharge the compensation network, and the fet MP4 will not generate current.

As shown in fig. 9, since the output voltage slope sampling module 40 charges the compensation network, the rising speed of the signal Vea increases, the inductor current rapidly rises to the load current during a heavy load, and the time t1 greatly decreases, thereby effectively reducing the undershoot of the output voltage V0.

As shown in fig. 10, since the output voltage slope sampling module 40 discharges to compensate the network, the falling speed of the signal Vea increases, the inductor current rapidly drops to the load current during light load, and the time t1 greatly decreases, thereby effectively reducing the overshoot of the output voltage V0.

Therefore, the invention starts from changing the rising and falling speeds of the output signal of the error amplifier EA, shortens the change speed of the inductive current, converts the change of the output load current into the internal current by detecting the change rate of the output voltage V0 in a specific time period and directly charges and discharges the compensation network of the output signal of the error amplifier EA, thereby rapidly improving the duty ratio without introducing small signal components and further simplifying the circuit design.

An embodiment of an application method of a BOOST circuit for improving transient response comprises the following steps:

the invention provides an application method of a BOOST circuit for improving transient response, wherein the BOOST circuit adopts the BOOST circuit, and the method comprises the following steps: the rising slope or the falling slope of the output voltage V0 in the turn-off time of the switching device is dynamically sampled according to the load change condition, the sampled rising slope or the sampled falling slope is converted into a current signal and then discharged or charged for a compensation network at the output end of an error amplifier EA, the duty ratio is rapidly reduced or increased, the overshoot or the undershoot of the output voltage V0 is reduced, and the transient response speed of the output is accelerated.

Further, when the load jumps from a light load to a heavy load, the output voltage slope sampling module 40 samples the falling slope of the output voltage V0 within the turn-off time of the switching device, converts the sampled falling slope into a current signal, and then directly charges the compensation network of the output end signal Vea of the error amplifier EA, so as to rapidly pull up the signal Vea, and rapidly improve the duty ratio. When the inductor current gradually rises and is greater than the load current, the output voltage V0 does not drop any more within the off time of the switching device, and the slope of the output voltage V0 within the off time of the switching device is sampled to be zero by the output voltage slope sampling module 40. It can be seen that, in this embodiment, an output voltage slope sampling module 40 is added, and when a load jumps from a light load to a heavy load, the module samples a falling slope of the output voltage V0 within a turn-off time of the power switch tube BG, and directly charges the compensation network of the signal Vea after the falling slope is converted into a current, so as to rapidly pull up the signal Vea and improve the duty ratio. When the inductive current rises to be larger than the load current, the output voltage V0 does not drop within the turn-off time of the power switch tube BG, so that the slope of the sampled output voltage V0 becomes 0, no slope conversion current is used for charging the compensation network, and the loop stability of the circuit in normal operation can not be disturbed in the transient change process.

Further, when the load jumps from a heavy load to a light load, the output voltage slope sampling module 40 samples the rising slope of the output voltage V0 within the turn-off time of the switching device, converts the sampled rising slope into a current signal, subtracts a threshold value, and directly discharges for the compensation network of the output end signal Vea of the error amplifier EA, so as to rapidly pull down the signal Vea, and rapidly decrease the duty ratio. After the inductor current gradually decreases and is smaller than the load current, the output voltage V0 is the rising slope of the load when the load is unchanged during the off time of the switching device. Therefore, when the load jumps from a heavy load to a light load, the module samples the rising slope of the output voltage V0 in the turn-off time of the power switch tube BG, converts the sampling voltage into current, and directly discharges for the compensation network of the signal Vea after subtracting a certain threshold (the rising slope of the output voltage when the load is unchanged), so that the signal Vea is quickly pulled down, and the duty ratio is reduced. When the inductive current is reduced to the load current, the output voltage V0 only has the rising slope when the load is unchanged within the turn-off time of the power switch tube BG, so that the slope conversion current is not needed to be the compensation network discharge, and the loop stability when the circuit normally works can not be interfered by the transient change process.

Therefore, the method for improving the transient response of the BOOST load is used for improving the transient response of the BOOST load and has high engineering practical value; the method can determine the speed of the change of the Vea according to the size of the load jump, so the application range is wider, and the circuit structure is simple and practical; the method of the invention can not introduce small signal components to the loop, thereby not influencing the loop stability.

It should be noted that the above is only a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept also fall within the protection scope of the present invention.

Claims

1. A BOOST circuit for improving transient response, comprising:

a BOOST converter for generating an output voltage higher than the input voltage;

the current sampling module is connected to the BOOST converter and used for generating a current detection signal;

the switching device is connected to the BOOST converter and is controlled to be switched on and off by a PWM (pulse width modulation) signal;

the control unit is connected to the BOOST converter and used for generating a PWM (pulse-width modulation) modulation signal under the action of a reference voltage, a voltage feedback signal of an output voltage, a rising slope or a falling slope of the output voltage, a current detection signal and a slope compensation voltage and generating a modulation signal with a preset duty ratio in a set time period;

the output voltage slope sampling module is connected with the control unit, is connected with the BOOST converter and is used for sampling the rising slope or the falling slope of the output voltage within the turn-off time of the switching device;

the output voltage slope sampling module comprises an operational amplifier OP, a field effect transistor MN0, a field effect transistor MN1, a field effect transistor MN2, a field effect transistor MP1, a field effect transistor MP2, a field effect transistor MP3, a field effect transistor MP4 and a field effect transistor MP5, wherein the non-inverting input end of the operational amplifier OP is connected with the output voltage V0, the inverting input end of the operational amplifier OP is connected with the source electrode of the field effect transistor MN0, the output end of the operational amplifier OP is connected with the gate electrode of the field effect transistor MN0, the drain electrode of the field effect transistor MN0 is connected with the drain electrode of the field effect transistor MP1, the gate electrode of the field effect transistor MP1 and the gate electrode of the field effect transistor MP2, the gate electrode of the field effect transistor MP2 is connected with the gate electrode of the field effect transistor MP3, the gate electrode of the field effect transistor MP4 is connected with the gate electrode of the field effect transistor MP5 through a switch SW1, and a capacitor C2 is connected between the gate electrode of the field effect transistor MP5 and the source electrode, the gate of the field effect transistor MN1 is connected with the gate of the field effect transistor MN2 through a switch SW2, a capacitor C3 is connected between the gate and the source of the field effect transistor MN2, the source of the field effect transistor MN0 is connected with a current source I and a capacitor C1, the drain of the field effect transistor MP2 and the drain of the field effect transistor MP4 are connected with the current source I, the drain of the field effect transistor MP3 and the drain of the field effect transistor MN1 are connected with the current source I and a current source Im, wherein the current source I is a fixed current source and is mainly used for providing bias current for a circuit to establish a direct current working point; the current source Im is preset current of an output voltage rising slope when the switch device is switched off when the output load is not moved;

the field-effect transistor MP1, the field-effect transistor MP2 and the field-effect transistor MP3 are sequentially connected to form a current mirror structure, the field-effect transistor MP4 and the field-effect transistor MP5 are connected to form the current mirror structure, and the field-effect transistor MN1 and the field-effect transistor MN2 are connected to form the current mirror structure.

2. The BOOST circuit of claim 1, wherein:

the BOOST converter comprises a voltage input end and a voltage output end, wherein the voltage input end is connected with an input voltage, the input voltage is processed by the BOOST converter and then is output by the voltage output end, the voltage input end is connected with an input capacitor, a first inductor and the switch device, and the voltage output end is connected with an output capacitor and an output load.

3. The BOOST circuit of claim 2, wherein:

the control unit comprises a logic control module, a driving module, an error amplifier and a voltage comparator, wherein the inverting input end of the error amplifier is connected with a voltage feedback signal, the non-inverting input end of the error amplifier is connected with a reference voltage, the output end of the error amplifier is connected with the non-inverting input end of the voltage comparator, the inverting input end of the voltage comparator is connected with a current detection signal and a slope compensation voltage, the output end of the voltage comparator is connected with the logic control module, and the logic control module is connected with the driving module.

4. The BOOST circuit according to any one of claims 1 to 3, wherein:

the switching element is a power switching tube controlled by the PWM signal to be switched on and off and is connected to the current sampling module.

5. The BOOST circuit of claim 2, wherein:

the voltage feedback signal is generated through a feedback network, the feedback network is mainly formed by a resistance voltage division circuit, and the resistance voltage division circuit is connected to the voltage output end.

6. A method of using a BOOST circuit to improve transient response, the BOOST circuit being a BOOST circuit according to any of claims 1 to 5, the method comprising the steps of:

according to the load change condition, the rising slope or the falling slope of the output voltage in the turn-off time of the switching device is dynamically sampled, the sampled rising slope or the sampled falling slope is converted into a current signal and then is discharged or charged for a compensation network of the output end of the error amplifier, the duty ratio is rapidly reduced or improved, the overshoot or the undershoot of the output voltage is reduced, and the transient response speed of the output is accelerated.

7. The method of application according to claim 6, characterized in that:

when the load jumps from light load to heavy load, the output voltage slope sampling module samples the falling slope of the output voltage in the turn-off time of the switching device, converts the sampled falling slope into a current signal and then directly charges a compensation network of an output end signal Vea of the error amplifier, quickly pulls up the signal Vea and quickly improves the duty ratio.

8. The method of application according to claim 7, characterized in that:

when the inductive current gradually rises and is larger than the load current, the output voltage does not fall within the turn-off time of the switch device, and the slope of the output voltage within the turn-off time of the switch device is sampled to be zero by the output voltage slope sampling module.

9. The method of application according to claim 6, characterized in that:

when the load jumps from heavy load to light load, the output voltage slope sampling module samples the rising slope of the output voltage in the turn-off time of the switching device, converts the sampled rising slope into a current signal and subtracts a threshold value, and then directly discharges for a compensation network of an output end signal Vea of the error amplifier, and the signal Vea is quickly pulled down, so that the duty ratio is quickly reduced.

10. The method of application according to claim 9, characterized in that:

when the inductive current gradually decreases and is smaller than the load current, the output voltage in the turn-off time of the switching device is the rising slope of the output voltage when the load is unchanged.